Posted price mechanisms constitute a widely used way of selling items to strategic consumers. Although suboptimal, the attractiveness of these mechanisms comes from their simplicity and easy implementation. In this talk, we discuss the performance of posted price mechanisms when customers arrive in an unknown random order. We compare the expected revenue of these mechanisms to the expected revenue of the optimal auction in two di‚fferent sett‹ings. Namely, the nonadaptive sett‹ing in which all off‚ers are sent to the customers beforehand, and the adaptive setting in which an offer is made when a consumer arrives. For the nonadaptive case, we show a strategy that achieves an expected revenue within at least a 1-1/ e fraction of that of the optimal auction. Moreover, this bound is tight, even if the customers have i.i.d. valuations for the item. For the adaptive case, we exhibit a posted price mechanism that achieves a factor 0.745 of the optimal revenue, when the customers have i.i.d. valuations for the item. These results also extend to the prophet inequality se‹tting. In particular, the adaptive mechanism for i.i.d. random valuations resolves an open problem posed by Hill and Kertz in 1982.